1

MICR 201 Microbiology for Health Related Sciences

Lecture 15: Microbial diseases of the cardiovascular and lymphatic systemEdith Porter, M.D.

2

Lecture outline Cardiovascular and lymphatic systems Bacterial diseases

Sepsis and septic shock, infections of the heart, rheumatic fever, systemic diseases caused by bites and scratches, vector transmitted diseases

Viral diseases Hemorrhagic fevers

Protozoan diseases Malaria, Chagas disease

Helminthic diseases Schistosomiasis

3

The Cardiovascular and lymphatic system (1) Blood (plasma and formed elements)

—Transports nutrients to and wastes from cells

Plasma leaves blood system to become interstitial fluid

Lymph capillaries—Transport interstitial fluid to blood

Lymph nodes—Contain macrophages, dendritic cells, B cells and T cells

4

The Cardiovascular and lymphatic system (2)

5

Sepsis and septic shock Septicemia

Presence of bacteria in blood with severe symptoms

Sepsis Bacteria present (and proliferating) in

blood and dissemination into various with organ dysfunction

Induces a systemic inflammatory response syndrome

Severe sepsis Sepsis + decreased blood pressure

Septic shock Sepsis + low blood pressure cannot be

controlled

6

Lymphangitis may accompany sepsisLymphangitis

Inflamed lymph vessels accompanying septicemia and septic shock

7

Sepsis Gram-negative sepsis

Endotoxins (LPS) induces cytokine release by macrophages and subsequently causes blood pressure to decrease

Antibiotics can worsen condition by killing bacteria and liberating endotoxin

Gram-positive sepsis Less often Less severe Lipoteichoic acids in the gram positive cell wall can also

induce cytokine release and symptoms of sepsis but to a lesser degree

Mostly observed during nosocomial infections▪ Staphylococcus aureus▪ Enterococcus faecium and E. faecalis

Puerperal spesis

8

Bacterial infections of the heart Endocarditis

Inflammation of the endocardium Subacute bacterial endocarditis

Alpha-hemolytic streptococci from mouth

Acute bacterial endocarditis Staphylococcus aureus from mouth

Pericarditis Streptococci

9

Bacterial infections of the heart: endocarditis

10

Consequences of endocarditis

11

Rheumatic Fever Inflammation of heart valves and joints Autoimmune complication of Streptococcus

pyogenes infections

12

Brucellosis (undulant fever)

Brucella, gram-negative rods that grow in phagocytes Granulomas form If bacteria are not controlled they can reenter the

bloodstream andcause recurrent B. abortus (elk, bison, cows) B. suis (swine) B. melitensis (goats, sheep, camels) Undulating fever that spikes to 40°C each evening Transmitted via milk from infected animals or

contact with infected animals

13

Selected diseases transmitted by scratches and bites

Bartonella henselae: cat-scratch disease

Pasteurella multocida: animal bites

http://www.lib.uiowa.edu/hardin/md/pictures22/dermnet/cat_scratch_disease_8.jpg

14

Animal bites and scratches: Pasteurella multocida

Normal microbiota of the upper respiratory tract of a number of animals

A frequent cause of opportunistic infections in domestic livestock

Usually acquired by humans from the bite or scratch of a dog or cat

Infection develops at the site of the wound and can spread via the lymphatics or via blood stream to a number of other organs

Virulent strains are encapsulated, but no other virulence factors are known

The organism is unusually sensitive to penicillin

15

Rickettsia infections Epidemic typhus

Rickettsia prowazekii Reservoir▪ Rodents

Vector▪ Lice (Pediculus

humanus corporis) Transmitted when

louse feces is rubbed into bite wound

Rocky Mountain spotted fever Rickettsia rickettsii Measles-like rash

except that the rash appears on palms and soles too

Vector▪ Ticks

16

Rocky Mountain Spotted Fever Rickettsia are obligate intracellular

parasites Infect and grown in endothelial cells of the

vascular system

17

Rocky Mountain Spotted Fever cases 1997 - 2002

18

Plague Causative agent: Yersinia pestis, gram-

negative rod Reservoir

Rats, ground squirrels, prairie dogs Vector

Fleas Bubonic plague

Bacterial growth in blood and lymph Septicemia plague

Septic shock Pneumonic plague

Bacteria in the lungs▪ Necrotizing hemorrhagic pneumonia

Human to human transmission▪ Black Death in the middle ages

19

Boubonic plague and US plague cases between 1970 - 2004

Lyme DiseaseCausative agent: Borrelia

burgdorferiReservoir: DeerVector: Ticks

Clinical stages of Lyme disease

Acute: Bull's-eye rash, fever, muscular and joint pain, meningeal irritation

Chronic : Disabling arthritis, myocarditis, meiningoencephalitis

Lyme disease in the U.S., 2005

23

Viral hemorrhagic fever Yellow fever

Liver cells are primary target Dengue fever

4 serotypes Infection with a second

serotype can lead to severe manifestation

Ebola virus High mortality rate of 60 –

80% within a few days

Malaria

Caused by Plasmodium species: P. vivax P. ovale P. malariae P. falciparum

Vector: Anopheles mosquito Definitive host: Anopheles mosquito

Malaria

Malaria in the United States

Malaria

Chagas’ Disease (1) American

trypanosomiasis Causative agent

Trypanosoma cruzi Reservoir: Rodents,

opossums, armadillos Transmitted via feces

of kissing bug Infects organs,

chronic infection, organ megaly

Chagas ‘Disease (2) Endemic in Mexico, Central America, and South America

~ 8 to 11 million people are infected Local lesion (chagoma, palpebral edema) at the site of

inoculation Acute phase (2 -3 months)

Usually asymptomatic If symptomatic:

▪ Fever, anorexia▪ Lymphadenopathy▪ Mild hepatosplenomegaly▪ Myocarditis

Asymptomatic chronic stage (years- decades) Symptomatic chronic stage

Cardiomyopathy (the most serious manifestation) Megaesophagus Megacolon Weight loss Can be fatal

30

Schistosomiasis

Infection of venous system by the trematode Schistosoma

Complex life cycle Pathology mainly

due to eggs that protrude into body cavities

Eggs

Miracidia

Sporocysts

Cercariae

AdultsSnail

Human

Life cycle of Schistosoma

Schistosomiasis Tissue damage (granulomas) in

response to eggs lodging in tissues

Species Adults Excretion of eggs

Affected regions

S. haematobium

Venous plexus ofurinary bladder

Urine(bladder cancer)

Africa, Middle East

S. japonicum Mesenteric veins

Feces East Asia

S. mansoni Mesenteric veins

Feces African, Middle East, South American, Caribbean

Types of Schistosomiasis

34

Important to Remember Cardiovascular and lymphatic systems are in

continuous comminucation Bacterial diseases: Sepsis and septic shock, infections of the

heart: endocarditis; rheumatic fever- an autoimmune disease after streptococcal infection; undulating fever caused by brucellosis; systemic diseases caused by bites and scratches: cat scratch disease and Pasteurella infection; vector transmitted diseases: plague, Lyme disease, Rocky Mountain spotted fever, typhus

Viral diseases Hemorrhagic fevers: Yellow fever, Dengue fever, Ebola

hemorrhagic fever (60 – 80% mortality) Protozoan diseases: Malaria caused by Plasmodium and

infects erythrocytes; Chagas disease caused by Trypanosoma cruzi leading to organ infection and organ megaly

Helminthic diseases: Schistosomiasis : adult couple lives in venous system, , pathology due to eggs that penetrate into urinary bladder or intestine.

35

Check your understanding

1) Which of the following statements about severe sepsis is false?A) Symptoms include fever and decreased blood pressure.B) Lymphangitis may occur.C) Symptoms are due to bacterial endotoxin.D) It usually is caused by gram-positive bacteria.E) It may be aggravated by antibiotics.2) Which of the following is NOT caused by a bacterium?A) Epidemic typhusB) Tickborne typhusC) MalariaD) PlagueE) Relapsing fever3) Human-to-human transmission of plague is usually byA) Rat flea.B) Dog flea.C) The respiratory route.D) Wounds.E) Unsanitary conditions.